1. Field of the Invention
The present invention relates to an inner diameter saw slicing machine used for cutting semiconductor ingots.
2. Description of the Prior Art
The semiconductor ingot 10 has a cone-shaped tail portion 10b and a cone-shaped head portion 10c formed on the ends of the cylindrical body portion 10a. The semiconductor ingot 10 as shown in FIG. 5B is transported in the direction of its axis over the feed rollers 12 and 14 which are arranged in a V formation. Then it is pressed down and secured by the clamper 16 at the position shown in FIG. 5A.
In the rotor 18, the outer circumference portion of the blade 19 is held in the tension head 24. In the blade 19, an inner circumference cutting edge 22 is formed by bonding diamond abrasive grain onto the inner circumference portion of the thin ring-shaped metal base 20. For example, the thickness of the metal base 20 may be 180 .mu.m and the thickness of the inner circumference cutting edge 22 may be 430 .mu.m. The rotor 18 is driven and rotated by a motor not shown. When the rotor 18 is lowered in this state, the end of the semiconductor ingot 10 is cut off as shown by the two-dot chain line. During this cutting, a liquid coolant, which may be plain water or a water solution of a surface active agent, is sprayed on the inner circumference cutting edge 22 from a liquid-emitting nozzle not shown. This liquid coolant travels along the direction of the rotation of the inner circumference cutting edge 22, enters the notch of the partially cut portion of the semiconductor ingot and is spread over both sides of the metal base 20.
Because of this, when the cutting of the tail portion 10b is completed, the tail portion 10b adheres to the metal base 20 due to the film-like liquid coolant between the metal base 20 and the tail portion 10b and the rotation force of the metal base 20 is thereby communicated to the cut-off tail portion 10b via the coolant. This results in the tail portion 10b being propelled in the direction of the rotation of the metal base 20. At this time, since the degree of adhesion to the metal base 20 and the force received from the metal base 20 in the direction of its rotation become greater in proportion to the size of the contact surface of the tail portion 10b and the metal base 20, the tail portion 10b will be so propelled even when the diameter of the body portion 10a is large and also the weight of the tail portion 10b is great. The weight of the tail portion 10b varies depending upon the diameter of the body portion 10a; it typically ranges from 1.5 to 8.5 kg.
As the tail portion 10b being propelled outward presents a certain danger, a barrier 26 is provided on the side where the tail portion 10b is propelled so that the tail portion 10b hits the barrier 26 and drops down to be collected in a collection box which is located below not shown.
However, sometimes the tail portion 10b may be bounce off the barrier 26 as indicated with the arrow in the figure and on the rebound it may hit the blade 19 and deform it. This greatly reduces the service life of the blade 19.
In order to deal with this problem, the tail portion 10b is cut while it is being held by a vacuum chuck 28 in the prior art, as shown in FIG. 6.
Because there are crystal habit lines as well as protuberances and depressions on the surface of the tail portion 10b, when the tail portion 10b is to be held by the vacuum chuck 28, it is necessary to make fine adjustments of the shaft center of the vacuum chuck 28 manually for each semiconductor ingot 10, and this prevents full automation of the cutting operation.
The problems described above also occur during cutting of the head portion 10c.